The decision to send out notifications is made in the service check and host check logic. Host and service notifications occur:

When a HARD state change occurs.

When a host or service remains in a HARD non-OK state and the time specified by the notification_interval option in the host or service definition has passed since the last notification was sent out (for that specified host or service).

Each host and service definition has a contact_groups option that specifies which contact groups receive notifications for that particular host or service. Contact groups can contain one or more individual contacts.

When Alignak sends out a host or service notification, it will notify each contact that is a member of any contact groups specified in the contact_groups option of the service definition. Alignak is aware that a contact may be a member of more than one contact group, so it removes duplicate contact notifications before it does anything.

Just because there is a need to send out a host or service notification doesn’t mean that any contacts are
going to get notified. There are several filters that potential notifications must pass before they are
deemed worthy enough to be sent out.

Even then, specific contacts may not be notified if their notification filters do not allow for the notification
to be sent to them. Let’s go into the filters that have to be passed in more detail…

The first filter that notifications must pass is a test of whether or not notifications are enabled on a program-wide basis. This is initially determined by the enable_notifications directive in the main configuration file, but may be changed at runtime through external commands. If notifications are disabled on a program-wide basis, no host or service notifications can be sent out.

If they are enabled on a program-wide basis, there are still other tests that must be passed…

The first filter for host or service notifications is a check whether the host or service is in a period scheduled downtime. It it is in a scheduled downtime, no one gets notified. If it isn’t in a downtime period, it gets passed on to the next filter. As a side note, notifications for services are suppressed if the host they’re associated with is in a period of scheduled downtime.

The second filter for host or service notification is a check whether the host or service is flapping (if flapping detection is enabled). If the service or host is currently flapping, no one gets notified. Otherwise it gets passed to the next filter.

The third host or service filter that must be passed is the host or service specific notification options. Each service definition contains options that determine whether or not notifications can be sent out for warning states, critical states, and recoveries. Similarly, each host definition contains options that determine whether or not notifications can be sent out when the host goes down, becomes unreachable, or recovers. If the host or service notification does not pass these options, no one gets notified. If it does pass these options, the notification gets passed to the next filter…

Notifications about host or service recoveries are only sent out if a notification was sent out for the original problem. It doesn’t make sense to get a recovery notification for something you never knew was a problem.

The fourth host or service filter that must be passed is the time period. Each host and service definition has a notification_period option that specifies which time period contains valid notification times for the host or service. If the time that the notification is raised does not fall within a valid time range in the specified time period, no one gets contacted. If it falls within a valid time range, the notification gets passed to the next filter…

If the time period filter is not passed, Alignak will reschedule the next notification for the host or service (if its in a non-OK state) for the next valid time present in the time period. This helps ensure that contacts are notified of problems as soon as possible when the next valid time in time period arrives.

The last set of host or service filters is conditional upon two things:

a notification was already sent out about a problem with the host or service at some point in the past and

the host or service remained in the same non-OK state that it was when the last notification went out.

If these two criteria are met, then Alignak will check and make sure the time that has passed since the last notification went out either meets or exceeds the value specified by the notification_interval option in the host or service definition.

If not enough time elapsed since the last notification, no one gets contacted. If either enough time elapsed and the two criteria for this filter were not met, the notification will be sent out!

Whether or not it is sent to individual contacts is depending upon another set of filters…

At this point the notification has passed the program mode filter and all host or service filters and Alignak starts to notify all the people it should. Does this mean that each contact is going to receive the notification? No! Each contact has his own set of filters that the notification must pass before they receive it.

Contact filters are specific to each contact and do not affect whether or not other contacts receive notifications.

The first filter that must be passed for each contact is the notification options. Each contact definition has options that determine whether or not service notifications can be sent out for WARNING, CRITICAL, or UNKNOWN states, recoveries and flapping. Each contact definition also contains options that determine whether or not host notifications can be sent out when the host goes DOWN, UNREACHABLE, or recovers. If the host or service notification does not pass this options filter, the contact will not be notified. If it does pass this options filter, the notification gets passed to the next filter…

Notifications about host or service recoveries are only sent out to a contact if a notification was sent out for the original problem. It doesn’t make sense that someone get a recovery notification for a problem he never was notified…

The last filter that must be passed for each contact is the time period test. Each contact definition has a notification_period option that specifies which time period contains valid notification times for the contact. If the time that the notification is being made does not fall within a valid time range in the specified time period, the contact will not be notified. If it falls within a valid time range, the contact gets notified!

You can have Alignak notify you of problems and recoveries pretty much anyway you want: pager, cellphone, email, instant message, audio alert, electric shocker, etc.

How notifications are sent depends on the notification commands that are defined in your objects definition files.

Notification methods (mail, paging, etc.) are not directly included into the Alignak code as it just doesn’t make much sense. The Alignak framework is not designed to be an all-in-one application.

There are a thousand different ways to do notifications and there are already a lot of packages out there that handle the dirty work, so why re-invent the wheel and limit yourself to a bike tire? Its much easier to let an external entity (i.e. a simple script or a full-blown messaging system) do the messy stuff. Some messaging packages that can handle notifications for pagers and cellphones are listed below in the resource section.

When crafting your notification commands, you need to take into account what type of notification is occurring. The $NOTIFICATIONTYPE$ macro contains a string that identifies exactly that.

The table below lists the possible values for the macro and their respective descriptions:

Value

Description

PROBLEM

A service or host has just entered (or is still in) a problem state. If this is a service notification, it means the service is either in a WARNING, UNKNOWN or CRITICAL state. If this is a host notification, it means the host is in a DOWN or UNREACHABLE state.

RECOVERY

A service or host recovery has occurred. If this is a service notification, it means the service has just returned to an OK state. If it is a host notification, it means the host has just returned to an UP state.

ACKNOWLEDGEMENT

This notification is an acknowledgement notification for a host or service problem. Acknowledgement notifications are initiated via the web interface by contacts for the particular host or service.

Alignak introduces optional hosts and services macros that add information about which impacts have an object and what to do. That can be useful when users that are notified, work for many customers and don’t know very well each services. So that help users without knowledge to take a decision about it.

There are 3 objects macros you can add on a host or a service object definition :